Rogue
by TenthWeasley
Summary: Set between the events of "The Idiot's Lantern" and "The Impossible Planet." Rose and the Doctor travel to a strange parallel world that Rose finds oddly familiar, and discover that even Hogwarts School of Witchcraft and Wizardry isn't free from alien life...
1. Chapter 1

"Right!" The Doctor clapped his hands together, staring down at where the small black video cassette had just popped back out of its slot. "That's that covered over, then. And the Wire should be gone forever!" He picked it up and tossed it into the air, smiling proudly. "I'm good. Oh, yes. I'm quite good."

"All right, I've got it. You're good." Rose Tyler crossed over to him and set her chin on the Doctor's shoulder, looking down at the innocuous-looking black plastic covering. "It's still the same thing my mum does if she's going to be out of the house when her programme's on."

"Oi! I'd like a bit of credit," he cried in mock offense, and Rose laughed, yanking the tape from his hands and bringing it a little closer to her face, studying it.

Tease him though she might, he'd saved her life – again – but it was hard, even after all this time, to get properly accustomed to the Doctor's day-to-day life, traveling around in the TARDIS, saving the world as if it were no more extraordinary than serving chips. And with video cassettes, no less.

Rose looked up and found the Doctor looking at her, grinning. "What?" she asked, laughing at him and thrusting the tape back at him.

"Rose Tyler, I like you much better with a face." He took the tape and flung it back into the depths of the TARDIS; it clattered to a stop somewhere out of sight. "Right, I'll probably need that again. I'll regret that." He clapped his hands again, rubbing them, as though to return warmth to his fingers. "So! Where to next, then?"

Rose gripped the edge of the control panel, leaning upon it and raising an eyebrow. "Well, speaking as someone who's been promised a trip to Barcelona for ages…"

The Doctor frowned. "Did I say that?" Rose shot him an exasperated look. "Ah! Well, you know, all that regeneration… stuff." He wiggled his fingers, as though that was what regeneration looked like. "Messes with the brain. Dogs with no noses, though, I do remember!" He leaped over to the panel and jabbed a button with his forefinger; the tiny bulbs on it light up bright white. "Barcelona it is!"

There was a familiar roaring sound as the Doctor yanked down on a lever, and the TARDIS shuddered beneath Rose's feet; she gripped the brass bar ringing the control panel even more tightly. From the other side, unseen but still audible over the sound of the TARDIS, the Doctor appeared to be hammering something with his fist to a rhythm she couldn't pick out.

"Next stop –" he began, but at that precise moment, there was another shudder, this one far less natural-feeling. Rose, who had grown used to the normal motion of the ship, was hurled sideways, crashing into the ground painfully and landing on her shoulder.

"What are you doing?" she yelled over the noise; some sort of alarm had just started flashing, and it was very difficult to hear herself think.

"Hang on!" The Doctor's face popped around the center column of the controls. "Something's sucking us elsewhere – I don't –" The ship gave another lurch, and the Doctor himself nearly went sprawling. "Just _hang on_!"

"There's nowhere else for me to _go_!" Rose screamed back, trying to get her elbows up underneath her. She did an odd sort of army crawl and managed to haul herself back into a standing position using the rail.

With an almighty crash, the TARDIS juddered to a halt, and Rose found herself back on the ground once more; miraculously, the Doctor was still standing. He was threading his fingers through his hair, squinting at the controls as though attempting to scry into the future.

Rose picked herself up again gingerly, checking for injuries; she was going to be sore for a while, more than likely, but thankfully nothing vital seemed to be broken. "Was that Barcelona?" she asked, a bit embarrassed to find that her voice was shaking slightly.

"No," the Doctor said, in a faint and faraway voice. He was starting to talk very quickly, which was a sure sign that he didn't expect her to be truly listening anymore. "It was like a magnetic pull – but we've still got power –" He laid a hand flat on the control panel, defying it to contradict him. "I don't think we're even in the same universe, but something pulled us here…"

He jogged over to the door and held out a hand behind him, waving for Rose to stay put. She crossed her arms, biting at her bottom lip, and waited for the all-clear.

"Rose." The Doctor's head was still poked out of the door of the TARDIS. "I think you're going to want to see this."

"What?" She crossed over behind him, ducking her head and sticking it out just below his, wrapping her fingers around the edge of the door. "And what do you mean, we're not in the same universe? Did you –"

She stopped mid-sentence. There was a small cluster of people gathered around the TARDIS in a half-moon, whispering among themselves and pointing inquisitive fingers at the blue box. They were all dressed more or less alike, in black robes decorated with small patches on the left breast. The TARDIS had landed in a large stone hall, and for a wild second, Rose thought that maybe they'd landed in some sort of cathedral run by teenage monks.

Then one of the people in front of her turned so that she could see the patch on his robe more clearly, and her mouth dropped open. It was yellow and red, and decorated with a lion. Rose gasped, and all of the onlookers' eyes swiveled to her at once; she resisted the urge to clap her hand over her lips.

"Excuse me – _excuse_ me, I'm a prefect, let me through –" A girl with bushy brown hair pushed through two of the boys at the front, who were staring at the TARDIS like fish out of water, eyes popping and mouths gaping. The girl was followed by a boy with a shock of messy black hair and bright green eyes behind glasses, and behind him was an even taller boy, who was so thin and gangly he looked like he'd been artificially stretched.

"Oh, but this is _brilliant_!" From somewhere above Rose's head, the Doctor couldn't have sounded more delighted with how events were turning out. "And you're all – oh, this is excellent, just fantastic." Stepping back, he opened the door out of the TARDIS a bit wider and stepped out of it, shoving his hands into the pockets of his coat and beaming at the gathered crowd in front of them.

"Who are you?" The boy with the messy black hair had broken away from the group, and had pulled a thin wooden stick from the pocket of his robes. Rose blinked, but she wasn't imagining things.

"Ah, yes, well." The Doctor grinned, hands still fisted in his pockets. "I'm the Doctor, and this" – he gestured at Rose from inside his pocket, so that his coat flapped oddly – "is my plus-one, Rose Tyler."

"Hello," Rose said weakly, wiggling her fingers at them all in a vague gesture. Nobody said it back. She hastened over to the Doctor and yanked on the sleeve of his coat. "Am I imagining things? Are we _actually_ –"

"Yup," he said happily. "Brilliant, isn't it?" He pointed at the black-haired boy, still motioning from inside his pockets. "You're Harry Potter, aren't you?"

"I –" Harry began, but the Doctor had already moved on.

"And it's Hermione Granger and Ron Weasley! _Fantastic_," he crowed. Now more of the faces gathered around the TARDIS and the Doctor and Rose showed alarm, rather than confusion or surprise.

"But you're not supposed to be real!" Rose said, before she could stop herself. A rather offended look came across all three faces at the suggestion. "You're just – you're just –" She looked wildly at the Doctor, who was still beaming, as though this was the best thing he'd ever seen in his life.

Harry Potter stepped forward again, his stick – his wand, Rose saw now – still trained on the pair of them. "How did you get here?" he asked suspiciously. "How do you know who we" – he vaguely motioned at himself and the two standing on either side of him – "are?"

"_That_ is a very good question." The Doctor scratched the back of his head, squinting up at the distant vaulted ceiling. "Which, quite frankly, I'd like the answer to." He sniffed, looking about him. "You lot haven't been messing with gravitational vortexes, have you? Intergalactic contact equipment all up to snuff?"

"He's starkers," Rose heard Ron lean over and mutter to Hermione.

"But you're a kids' book," Rose blurted out, still not quite over the fact that Harry Potter had sort of just materialized in front of her. "You're not supposed to be _real_."

Harry blinked at her. "I'm a what?"

"Now, don't be rude," the Doctor chided, rocking backward and forward on his feet, hands clasped behind his back. "Can I have a word with your headmaster? Dumbledore, isn't it?" But as soon as he asked the question, Rose saw the three of them exchange a very significant look amongst themselves.

"He's on the run," said Ron in a low voice. Hermione made a disapproving sort of noise, but he flapped a hand at her, motioning her into silence. "And I don't think you'll want to talk to Umbridge."

Harry gave a great snort of disbelief at that. "But we can take you to McGonagall," he added, and this time it was he who was on the receiving end of Hermione's noise of displeasure. "She'll know what to do," he protested.

"Yes, but we're going to be late for History of Magic as it is," she snapped. "We don't have time to –"

"I'll go and meet up with you two later," Harry said firmly, turning back to look at the Doctor and Rose, who had been watching the exchange mildly. Ron looked rather put out that it wasn't his good fortune to be missing the beginning of a history lesson, but there wasn't much room for arguing the point.

The rest of the small knot of students who had been staring at the TARDIS, and at the Doctor and Rose, began to disperse now for their own lessons, muttering amongst themselves and chancing glances back at the strangers in the middle of the entrance hall. Rose felt a bit like she was on display; she tugged self-consciously at the bottom hem of her pink sweat top and cleared her throat.

"Doctor," she hissed. He turned around, beaming. "I don't… this isn't real, is it?"

"Oh, very much so." He grinned widely. "Isn't it fantastic?"

Rose was extremely unsure about how to respond to this, but there was no time to form a response even if she had been sure. Harry was waiting at the bottom of the staircase, looking a bit impatient, and the Doctor had already started moving off in his direction. Looking back at the TARDIS and blowing out a quick breath, Rose followed after them.


	2. Chapter 2

As soon as Rose had caught up to the Doctor, she took hold of his elbow, drawing him back down a step. "Look," she said, "I know this place, all right? These books are incredibly famous, Doctor. Kids all over the world read them. We can't have just… stepped into Hogwarts." But she said it more as a question; if there was one thing she had learned, traveling around with the Doctor, it was that the word _can't_ wasn't really a part of his vocabulary.

The Doctor's eyes flicked briefly to Harry's back. "I don't think he'd agree with you," he said. "Look, it's – it's a bit complicated."

"Well?" Rose folded her arms across her chest, although instantly regretted doing so, as she nearly tripped over an uneven stone step. "I'm listening." She briefly touched her teeth with the tip of her tongue, waiting for an explanation.

"It's – it's like –" The Doctor ran a hand through his hair, making it spring out all over the place. "Our universe isn't the only one, Rose, you know that. There are little pockets of space, all across time, and they sort of" – he formed his hands into a sphere in front of him – "weaken." The Doctor closed his hands together, the space between his fingers shrinking. "Those weak spots are prime places for traveling between universes, which is what we've just done. And the thing about those weak spots, those universes, is that there are an infinite number of them. Growing, changing." He twirled a finger at the air around them, indicating the castle. "We've got this one because of human ingenuity."

"Okay," Rose said slowly. "So… all books. Every book I've ever read – it's got its own little world, apart from the one I come from?"

"Exactly! And the thing is, our universe is probably just a story to them. Brilliant stuff, really." The Doctor shot her a pleased grin, but all Rose felt was the oncoming effects of what promised to be a nasty migraine. She didn't feel like thinking about pockets and parallels and whatever it was he was doing on about now, and shut up. It was crazy, it was mad – but she was here, and it definitely felt real. That was good enough for her.

Harry led the Doctor and Rose up the broad marble staircase without saying a word to them, and she had no idea if that was a good thing or not. They stopped before they had gone far enough to make the heavy silence awkward, however, in front of a tall wooden door with no apparent knob. Harry knocked loudly on it, and there was a shuffling sound as someone moved to open it.

"Yes? What do you want?" Minerva McGonagall looked at all her visitors imperiously, her sharp eyes boring into them from behind her stout, square spectacles. They flicked over the Doctor and Rose with a puzzled expression, and finally landed on Harry. Seeming as though she were grasping the one thing that made sense to her as far as the motley crew who had just appeared outside her office, she asked, "Potter? Can I help you?"

Harry flapped a hand in the general direction the other two were standing. "They asked to see you," he said uncertainly.

"And who are they?" McGonagall asked, folding her mouth into a firm line and not budging an inch from the doorway. Before Harry could open his mouth again, the Doctor stepped neatly around him, sliding his sonic screwdriver into his pocket and proffering a hand for the Transfiguration professor to shake.

"Hello," he beamed happily. "I'm the Doctor, and this is Rose, my – we just did this," he interrupted himself, frowning and looking over his shoulder at Rose. She shrugged helplessly back in reply.

"_The_ Doctor?" McGonagall asked, her lips thinning more than ever.

"That's right. And Rose," the Doctor added helpfully. "Thing is, we really have no earthly clue why we're here, and we were wondering if you might, ah… be able to enlighten us." He rocked back on the balls of his feet. "I asked if anyone had been messing with gravitational vortexes, but frankly the responses were less than desirable."

The woman in front of them seemed to come to some kind of decision; she nodded once, almost imperceptibly, and her nostrils flared. "Potter," she said, addressing Harry without looking directly at him, "you're late for History of Magic. Run along, please." Harry looked very much as though he wanted to stay to see what was going on, but arguing with McGonagall was apparently out of the question. He turned and trudged off reluctantly, hoisting his schoolbag higher on his shoulder.

Once he had gone, McGonagall opened her door wider to allow the Doctor and Rose enough space to pass through. "Come in," she said unnecessarily; the Doctor was already inside the room, fishing in his pocket for his screwdriver. Rose scurried through hastily, feeling as though she were back in school, about to be reprimanded for something.

The Doctor held his screwdriver aloft, the bulb on the end of it lit electric blue as it emitted its sonic waves. McGonagall was looking at it warily, and Rose intervened hastily, sitting down on one of the two hard wooden chairs sitting opposite her desk.

"Here's the thing," she blurted out. "We were headed somewhere completely different, and the TARDIS just sort of… spit us out here." She realized too late that this woman had no idea what a TARDIS was, and indeed, the look she was being given indicated that McGonagall thought her as mad as Rose thought this alternate universe was.

"Different universe, actually," the Doctor said, as though reading Rose's mind; he was standing by a large stone fireplace now. Whatever noise his screwdriver was making appeared unsatisfactory to him; he frowned, lifting his finger from the button and returning it to a hidden inside pocket. He leaned against the fireplace, crossing one ankle over the other and plunging his hands into the pocket of his suit. "Anything unusual happening about the place? Weird creatures your little wooden sticks can't get rid of?"

Rose shook her head minutely at him; he looked baffled, as though he didn't know he'd just said something slightly offensive. McGonagall's flared nostrils had turned rather splendidly white.

"As it happens," she said crisply, "I do know who you are, Doctor." Her hard eyes didn't even acknowledge Rose sitting in the chair in front of her; the professor motioned to the other one, but a little crease had appeared between the Doctor's eyebrows, above his glasses.

"Do you?"

"Yes." With a sigh, McGonagall seated herself and pressed the tips of her fingers together primly, surveying the Doctor from over them. "Professor Dumbledore has thought for some time now that we'd be seeing another of your kind. Hogwarts has played host to Time Lords before, being a very old school – though, of course, not for some time."

A sour expression was playing now around the Doctor's mouth. "No, it wouldn't be," he muttered, so only Rose could hear him. "Considering how long it's been since the Time War." He suddenly became vastly interested in his sonic screwdriver, clicking the button on the side rapidly, moving it through the air and squinting at it.

"Why did Dumbledore – sorry, _Professor_ Dumbledore," Rose amended hastily. Like most of the world, she'd read _Harry Potter_ before, but had apparently vastly underestimated just how terrifying the Head of House could be when she glared. "How did he know the Doctor was going to be stopping by? We didn't even know ourselves until about half an hour ago."

McGonagall's lips pursed, as though she'd just ingested a particularly sour lemon. It seemed to cost her something to say the next words. "There have been… incidents," she told the pair of them stiffly. "And quite frankly, Madam Pomfrey is baffled about how to deal with them. Professor Dumbledore believes that it is something beyond our magic, and has made dutiful note of the Time Lords from records of previous headmasters."

"Now, that's more like it," said the Doctor appreciatively. "Erm – not that that's a good thing," he added. "These incidents, that is. What's the problem?"

"Several students have been admitted to the infirmary since Professor Dumbledore has taken his leave," the older woman said carefully. "Red welts, pale skin, listless temperament – nothing Madam Pomfrey does seems to work on them. They do not worsen, but they do not heal. And more and more of them come in every day."

"Perhaps it's exam stress," Rose joked weakly.

McGonagall seemed to bristle at that. "We take this matter very seriously, Miss…?"

"Tyler," she said hastily. "Rose Tyler. But please, call me Rose."

McGonagall ignored this – indeed, apparently decided to ignore her completely. She turned her attention back to the Doctor, who was still leaning against the roaring fireplace, a curiously thoughtful expression having replaced his confused one.

"What sort of red welts are they?" he asked. "Lacerations, bruises, anything like that?"

"Like – like –" The deputy headmistress made an impatient noise through her teeth and rose swiftly, robes rustling about her. "Well, telling you will do no good, I suppose. Come with me, Doctor. I'll take you to the hospital wing."

* * *

Professor Binns was already droning on, well into the day's lesson, when Harry arrived in the stuffy classroom. Ron was nearly asleep over the top of his quill already; Hermione was scratching away busily on a roll of parchment, as always.

"What happened?" she hissed bossily as soon as Harry had sat down, not taking her eyes from the ghost at the front of the room. Harry bent over his bag and extracted a slightly squashed parchment roll of his own, though he knew it would only be used to play hangman with Ron in the end. Ron had perked up at his friend's entrance and looked just as eager to hear Harry's answer as Hermione was.

"I took them to McGonagall, that was it," he muttered, careful to make sure none of their classmates overheard. "She didn't want me hanging around."

"What d'you want to bet it's about those kids in the hospital wing?" Ron said darkly, stabbing absently at his notes, so that large ink blots bloomed across them. "Seamus said he saw one of them being carried off the other day. He had all these weird red marks on him, Seamus said. Like the giant squid had attacked him or something."

Hermione frowned, biting on the tip of the feather attached to her quill nib. "We could go to the library," she said slowly. "There's probably something in there about squid creatures, or maybe octopus half-breeds –"

"Hermione, Madam Pomfrey doesn't even know what's wrong with them," Harry interrupted her, eyes sliding to the front to make sure Professor Binns wasn't listening to them. "And she regrew all the bones in my arm, in case you've forgotten."

"Umbridge's probably got some new torture device to use on terrified first years," Ron opined. "Or it's Malfoy. That stupid Inquisitorial Squad's all over the place now."

"But they're not allowed – !" Hermione started to say, but Ron cut her off quickly.

"Hermione, since when has that lot ever played by the rules?"

"Still," she said hesitantly, "it's a bit strange, don't you think? That man, showing up in a creaky old blue police box? I don't think I trust him. He could be working for Umbridge or the Ministry, or even Voldemort –"

"Never mind him," said Ron, interrupting Hermione a second time. "I'm more interested in who he brought with him. Not bad-looking, is she?" He nudged Harry's shoulder. Hermione's cheeks turned oddly pink; with a mutter of something that sounded like "boys," she bent her head over her notes, and did not further contribute to the conversation.

"She's all right," Harry muttered, but his mind wasn't on the blonde girl who'd showed up in the middle of the entrance hall. He was much more interested in this man who called himself the Doctor, and where he'd come from in the first place. And why had Rose Tyler acted like Hogwarts was so strange, anyway? Granted, it was a school for wizards and witches, but there was clearly magic involved in getting her there in the first place…

Whatever else, he agreed with Hermione: He wasn't sure they were to be trusted.


	3. Chapter 3

There was one thing about rubber soles that the Doctor never could quite get used to. They were great for absorbing electricity, of course – hadn't they just saved his life doing that very thing? – but they made for rather loud squeaking sounds on stone floors. As he, Rose, and Professor McGonagall strolled along the Hogwarts corridors from the deputy headmistress's office to the hospital wing, he watched the older woman from the corner of his eye. Her lips were nearly invisible; clearly his squeaky shoes were noticed by her, as well.

Rose tugged on the sleeve of his coat, yanking him back a few steps to walk behind McGonagall. If she noticed, she didn't say anything. "What's so weird about this?" she muttered, tipping her head towards the woman in front of them. "Kids are bound to get all banged up, aren't they? What's a few bruises got her so worried about?"

"Dunno," he said, running a hand through his hair and squinting. He was still wearing his brainy specs, and they always gave him a slight headache, seeing as how he really didn't need to wear glasses at all. "Could be nothing. But then again" – he gave his companion a knowing sort of look – "anything that's got a witch concerned is worth a look, isn't it?"

Rose bit her lip, looking again towards McGonagall, marching staunchly in front of them. "So she's seriously real." It wasn't a question so much as a statement of her trying to wrap her head around matters. "Mickey is just _not_ going to believe –" But she stopped short. The Doctor felt a sort of twinge in his stomach thinking of Mickey, left behind in the parallel universe with Rose's dad, and all those cybermen…

"Here we are." McGonagall had stopped at the end of a short, narrow corridor, just a few paces from an opening in the stone wall. "Madam Pomfrey's in her office at the back. I'll run and fetch her." Her eyes flicked briefly over to Rose, and the Doctor sensed a slight bit of disapproval there. He bristled instinctively, but then she was gone.

As soon as her footsteps had retreated through the door, he poked his head around. Two rows of hospital beds lined a wide flagstone aisle. Most of them were empty, the starched white sheets pulled crisply up to meet limp pillows, corners tucked squarely under the mattresses. At the end of the ward, however, was a set of drawn curtains, hiding the occupants from view of the infirmary entrance.

The Doctor glanced back at Rose and pressed a finger to his lips, and then began to creep down the aisle, silently removing his screwdriver from his pocket. Rose, for a lack of anything better to do, followed after him.

_Squeak, squeak, squeak._

"You're making a lot of noise," Rose hissed, and he looked back at her again, pressing his finger more firmly in a gesture of quiet. He reached the curtains and peeked around the edge of them.

"Sir!"

The Doctor and Rose jumped guiltily in one motion, the screwdriver flying from his hands. It landed with a small _whump_ on the feet of the bed's occupant. McGonagall was now accompanied by a stern-looking witch in dull red robes with a patch emblazoned on the left breast; upon closer inspection, the Doctor saw it was two wands, forming the shape of a cross. Her gray hair was pulled high upon her head in a bun not unlike McGonagall's.

"Hello!" he said brightly. As smoothly as he could, he reached over and plucked his screwdriver from the student's feet. "I'm the Doctor, and –"

"She knows who you are," McGonagall said, arching an eyebrow high on her forehead. "Doctor, this is Madam Pomfrey, our school nurse." Madam Pomfrey nodded stiffly.

"Are you a proper doctor, then?" she asked at once. "Where did you do your training?"

The Doctor glanced askance at Rose; she looked as though she was badly holding back a laugh. "Ah," he said, a bit crestfallen. "Well. 'Training' is a bit of a funny word, isn't it?"

"His credentials are good enough for Professor Dumbledore, Poppy," McGonagall said in a low voice, craning her head around as though searching for eavesdroppers. "And therefore they are good enough for us." Madam Pomfrey looked as though she didn't much want to accept this logic, but it appeared there was no other option.

"This is one of the students," she said instead, moving around the pair in front of her and coming to the far side of the bed separated from the rest of the ward by its curtain. "Colin Creevey, poor dear. It does always seem to be him…"

A mousy-looking blond boy was asleep beneath the blankets. Setting her jaw, the nurse flipped them back to reveal him from the neck down. From behind the Doctor, Rose stifled a gasp.

His legs, his collarbone – and presumably much of the rest of him – was covered in bright red welts, like suckers from tiny sea creatures. _Squid or octopus? _the Doctor thought, frowning. He'd seen these somewhere before, somewhere in his nearly-thousand years of traveling, but where…?

He began moving his screwdriver over the boy's prone form, pressing the button on the side so that it whirred and flashed in a synchronic staccato. Behind him, he heard Rose speak to Madam Pomfrey and McGonagall, though he couldn't see her face.

"How long has it been since Professor Dumbledore's been gone?"

"About a week now, I should think," Professor McGonagall said. "He left no means of contact – although," the woman added, "I should see why. Professor Umbridge is terrified of him." The Doctor smiled slightly at the proud note that crept into her voice at that. "All of the Ministry is."

At that moment, the screwdriver in his hand hummed at a slightly different pitch, whirring intelligently. _Aha_, the Doctor thought triumphantly. He stepped back, lifting his finger from the screwdriver's button and slipping it back into an inner pocket of his suit.

"Well?" said the deputy headmistress expectantly.

"Makrenogs," the Doctor said, shoving his hands in his pockets as well and starting to rock back and forth on the balls of his feet. All three women's brows lowered over their eyes in confusion. "Those welts are from Makrenogs," he said by way of explanation, though it didn't appear to help. "They're dead stupid, actually. Keep getting enslaved by other alien races because they can't think for themselves." He grinned. Apparently, no one else found this amusing.

"Aliens?" Madam Pomfrey hissed to McGonagall in a horrified-sounding whisper.

"Then what are the welts for?" asked Rose. She took a few steps closer to the bed, peering at Colin's reddened skin with wary interest.

"That's what they do," the Doctor explained patiently. "They suck energy from people – not always humans, though you are brimming with energy." Rose beamed. "They harness that energy for whatever happens to be enslaving them at the time. Rather useful, as long as they're on your side."

Madam Pomfrey still sounded completely lost. "Suck…? Like dementors?"

The Doctor frowned. "Like what?"

"They suck the happiness out of people," Rose whispered. "In the books – I mean, in this world," she said, a bit more loudly, at a suspicious look from McGonagall. "They can suck out your soul through your mouth."

"I – well, I suppose they're sort of like that," the Doctor conceded. "They've got loads of suckers on their limbs. Leech out your energy right through your skin, and that causes these welts." He tapped Colin square in the middle of the forehead; the boy mumbled in his sleep, rolling over onto his side.

McGonagall stepped forward again, nostrils white with annoyance. "Be that as it may," she said crisply, "that doesn't quite explain how they came to be _here_."

"No, it doesn't." The Doctor frowned, rubbing at the puckered skin on his forehead. "Something had to have brought them here – and where are they hiding?" He looked around, as though expecting to see a few Makrenogs hanging from the ceiling by their wiry, sucker-covered arms. "They like damp, dark places –"

"You mean like a dungeon?" Rose interrupted.

The Doctor grinned. "_Exactly_ like a dungeon!" She beamed. He turned to McGonagall. "All right if I pop down there, then? Check it out a bit, see what's going on?"

"By all means," she responded, although didn't look extremely pleased at the idea of him patrolling the corridors in the middle of the school day. "As it happens, I've got a lesson to teach in the next hour, but –"

As though on cue, the door to the hospital wing slammed open, banging off the wall behind it. Harry, Ron, and Hermione all sauntered in, moving purposefully towards the group clustered by Colin Creevey's bed. The Doctor's eyes locked onto the tall, gangly redhead at the back of the group; his own gaze was fixed on Rose. Small needles of jealousy prickled his skin, and he shrugged them off hurriedly.

"Potter," McGonagall said exasperatedly. "Weasley. Miss Granger." For a minute, it looked as if she was going to tell them off, but apparently decided better. The Doctor smothered another smile; these three did always have to be in the thick of anything that smelled of adventure.

"What's going on, Professor?" Harry asked, coming to a stop at the end of the ward. Ron was now standing on tiptoe, having finally yanked his eyes away from Rose, and was trying to peer over at Colin. Madam Pomfrey yanked the sheets back up around his chin.

"The Doctor is taking matters into his hands," the deputy headmistress told them. "He's to head down to the dungeons –"

"I'll go," Harry volunteered. "He doesn't know where they are. I'll show him."

"You have class," McGonagall told him, arching her eyebrow. "My class, if I'm not mistaken."

"He's got to know where the dungeons are," Ron Weasley piped up helpfully from behind Harry. The black-haired boy nodded encouragingly.

"I –" She turned her head between the two, mouth fumbling for words. "Oh, _all right_," she snapped. "The sooner this is over, the better." She pointed a warning finger at Harry. "I still expect your homework on my desk Friday morning, as usual. And we'll not make this a habit."

The Doctor, who'd been watching this exchange wordlessly next to Rose, turned to her now. She looked up at him expectantly. "Right, we'll be back shortly," he said, talking quickly – he didn't want to give her room to argue. "Ten minutes. Just stay here and –"

"Hang on!" she interjected, frowning and folding her arms across her chest. "I'm coming with you!"

"Too dangerous," the Doctor said, insides squirming even as he did so. He never liked to leave Rose behind – but her safety was extremely important to him.

"I'll show you around the castle," Ron spoke up at once. "Hermione, too," he added, not missing the sharp look from the girl on his left. "Give you something to do."

"All right." Rose looked at the Doctor meaningfully, and he tried not to smile to break the seriousness of it. He loved her serious look. "Ten minutes, all right?"

He saluted her, and this time was sure a smile of her own tugged at the corners of her mouth. The Doctor turned to Harry, who was looking at him warily, hands folded around the strap of his bag across his chest. He could understand the boy's suspicion, anyhow; clearly he was used to investigating things on his own, not leading a stranger to do it for him. Then again, what did a few teenage wizards know about Makrenogs?

He gestured at the door to the hospital wing. "Shall we?"


	4. Chapter 4

A thick and rather uncomfortable silence pervaded the air as the Doctor and Harry sauntered through the castle, taking flight after flight of stairs, heading for the dungeons. The Doctor looked about him with interest, taking in the castle as fully as he could against Harry's unusually quick walk. There were no signs of Makrenog habitation here – but it was too light and dry for them anyway. _Good old Rose_, he thought happily, _thinking of the dungeons!_

Students passing in the corridors on their way to class gaped openly at the tall, oddly-dressed man walking beside Harry Potter, although Harry's life was odd enough that it almost seemed normal. The Doctor ignored them. He'd focused his attentions back on the boy beside him, wondering at the scowl on his face.

"Lessons going all right?" he asked, by way of making conversation.

"Yes," Harry responded in a surly voice. The topic died instantly, and the Doctor was just searching about for something else to say, hoping to not have to resort to the weather, when the teenager spoke up again. "So just who are you, anyway?"

"The Doctor." The man in question scratched the side of his nose, glancing subtly at Harry over the top of his hand. He didn't seem impressed. "A Time Lord, that's what my people are called," he continued. "I've come from very far away – so has Rose, actually, but I came even farther – and that blue police box, that's my TARDIS."

Harry wrinkled his nose in distaste. "And that's how you get around, is it?"

"Oh yes," the Doctor said cheerily, mistaking his questions for genuine interest. "'Time and Relative Dimension in Space'! Mind you," he added, the grin wiped from his face, "exactly how we wound up here's a bit of a problem. Something pulled us here. Your little Makrenog problem, yes, but what's controlling _them_?"

They'd reached the entrance hall by then; it was nearly deserted, most of the rest of the student body either in their common rooms or attending class by now. The Doctor gave the TARDIS a fond look as they passed it. He and Harry crossed to stand in front of the dark and narrow archway leading down to the dungeons. The stairwell beyond was almost pitch-black; the torches on the wall burned low in their brackets, not shedding much light at all.

"Dark," the Doctor observed, and distinctly heard Harry give a small snort of derision. He felt himself bristle with indignation, and forced himself to remain calm. "Good thing we've got this, though!" He lifted the sonic screwdriver from the pocket of his trenchcoat and pressed the button on the side. The opening to the dungeons was at once faintly lit with pulsating blue light.

Harry stared at it for a couple of seconds, and then, from a pocket in his own robes, he removed his wand. The Doctor watched him intently. "_Lumos_," Harry said, perhaps louder than was necessary, apparently unable to keep a note of pride from his voice as well. The end of the wand sparked bright white, drowning the screwdriver's light with its own brightness.

"Let's go," the teenager said, looking, the Doctor noted, noticeably happier. Sheepishly tucking the screwdriver back into his coat pocket, he followed Harry down the steps and into the dark warren of dungeon passages.

Water dripped somewhere unseen; from further down the corridor, the Doctor could hear a professor lecturing his students in a deep, slow voice. Even from this distance, the sarcasm in the speaker's voice was painfully obvious. But nothing appeared, at first glance, to be out of the ordinary – as far as anything could be out of the ordinary in a wizarding school, of course.

"What we're looking for," said the Doctor, careful to stay within the beam of Harry's wandlight as he stepped close to an adjacent wall, moving his sonic screwdriver over the wall, "is anything suspicious. Things that weren't there a couple of months ago, or something that's moved, or…?" He turned, hoping Harry would fill in the blank, but he just looked baffled.

"I… don't think anything's changed," he said, adding, with a small smirk, "I try not to spend a lot of time in the dungeons." He shrugged one shoulder and started walking; without an alternative, the Doctor followed him, still running the screwdriver over the walls they passed. "We could ask a Slytherin. Their common room's down here."

But the Doctor stopped abruptly, so that Harry had to veer away to avoid hitting him. The sonic screwdriver had chirped abruptly, and quickly the Doctor put his ear against it, ignoring the weird look the other gave him. He took a step back, squinting over the tops of his sadly useless glasses.

"What's this door?"

Harry glanced at it, and then did a quick double-take. "I've never noticed that," he said at last, after a long and rather tense silence. It seemed to cost him something to admit it. It was, admittedly, a very hole-in-the-wall sort of door, only half the size of the wall itself, and made of some metal that had been burnished to exactly mimic the color of the wall.

He raised his wand and came to stand alongside the Doctor. "_Alohomora_," he said firmly. Nothing happened. "Great," Harry muttered. "If it's locked with magic that even _Alohomora _can't get through –"

He was cut off; the Doctor raised his screwdriver, and, with a screech of protest from the metal door's hinges, it swung out to meet them, gaping ominously onto complete black. Harry's mouth dropped open before he could stop it. The Doctor grinned widely and flipped the screwdriver end over end, catching it again in his hand, before pushing his way into the dark room.

This was, of course, a mistake, because Harry didn't follow at once. Ink-black shadows pressed themselves like weights over the Doctor's eyes, but through the gloom he could already hear them: The soft, slow, moist sucking sound that Makrenogs emitted naturally when at rest. He wrinkled his nose, and Harry's wandlight finally appeared around the corner, revealing just what was in the room.

Makrenogs clung to the walls, great heaping masses of what looked like slightly melted gray rubber. Their beady black eyes were closed in sleep, but their tentacles still worked slowly, waving up and down as they extended from their bodies, jutting into the center of the room so that it looked like a tangled canopy of slimy gray vines. The gray of their flesh melded extraordinarily well with the stone walls. When the light hit them, a few of them shifted, but they stayed sleeping. The Doctor wasn't surprised; Makrenogs were, typically, night-dwelling creatures.

Behind the Doctor, Harry made a disgusted noise. "Is that what got Colin?" he asked in a horrified undertone.

"Yes," the Doctor said grimly. He didn't dare use his sonic screwdriver for fear of waking one or more of them up; besides, he very clearly knew what he was dealing with. "Fascinating creatures, but certainly," he added wryly, "not very pleasant to look at."

"You can say that again," Harry muttered. The Doctor jerked the younger boy back, steering his shoulder away from a stray Makrenog tentacle that had wandered while its owner was asleep. The tentacle snaked back in the other direction, meshing with some of its fellows.

"The thing I don't get," said the Doctor, becoming lost to his own thoughts, "is why they're here." He tilted his head as he stared at the alien creatures, rubbing his fingers along his jawline in concentration. "It's like I said: They're downright stupid, really." He let out a little groan of frustration. "Why here, why now…?"

Harry looked askance at the funny man beside him, apparently debating whether or not he was supposed to answer. "We've been getting a lot of rain?" he hedged at last; it came out more as a question than a possible solution.

"Nah, can't be it," the Doctor said dismissively. "This is Scotland, isn't it? Or a version of Scotland, anyway." He ignored Harry's affronted look. "Now, if you hadn't been getting _any _rain, I'd be more concerned…" His voice trailed away into thought once more.

"They've got to be working under someone's orders," he said at last. "Someone who's trying to harness the power of the witches and wizards here." The Doctor was speaking very fast now, building momentum as he puzzled out the solution he was seeking. "Obviously a school's a good place for that. Young blood, lots of it, but why –"

And abruptly, without any warning, he stopped talking. Harry shot him a panicked look, backing away a step, obviously fearing that the Doctor had seen something in one of the sleeping Makrenogs before them. But the Doctor wasn't thinking about Makrenogs anymore. His mind was far away, latched on one particular idea, an idea that should have been impossible, and yet it made _sense_...

"Oh no," he muttered.

"Sorry?" Harry said in slight alarm. "What's happened?"

But the Doctor had already turned, running out of the tiny hidden room and sprinting for the dungeon entrance. He heard the metal door fall shut with a _wham_ as Harry followed him, trainers padding along the stone floors. The Doctor had to get back upstairs, back to Rose and the rest of the school, before he discovered – too late – that he was right.

* * *

_A/N: I'm very sorry for how long it's taken me to update this story! Rest assured, three months was not my intention. I've been busy this summer finishing up the last of one of my Snape/OC novels, and then finishing up my second original novel, but both of those are now complete and I thought it was time to give a few of my small side projects some attention. So here – at last – is chapter four! Thank you for reading, reviewing, following, and/or adding this to your favorites!_


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